A wide variety of implantable medical devices (IMDs) are known in the art. In general, IMD sizes continue to be reduced, including a move towards smaller volume housings and smaller components within the IMD, while maintaining structural integrity and functionality of the devices.
Components that provide structural integrity to the IMD include frames. Conventional IMDs may include a frame made of rigid thermoplastic and other internal components generally being affixed to the housing with epoxy to lock the components into place. These IMD assemblies are subject to loose rattling of components in the device.
Of particular interest are IMDs that include electronics such as processors, capacitors, wiring, batteries, etc., which are subject to potential corrosion as a result of moisture within the IMD. Examples of such IMDs that include electronics include sensing or monitoring devices, signal generators (such as cardiac pacemakers or defibrillators), neurostimulators (such as spinal cord stimulators, brain or deep brain stimulators, peripheral nerve stimulators, vagal nerve stimulators, occipital nerve stimulators, subcutaneous stimulators, etc.), gastric stimulators, infusion devices, hearing implants, cochlear implants, vision implants, and the like.
To reduce any presence of moisture within the IMD after it has been hermetically sealed during the manufacturing process, desiccant materials have been included in such IMDs to absorb at least some of the moisture present, including moisture released from plastic components in the IMD after the IMD is hermetically sealed. Traditionally, a thermoset polymer, such as silicone, has been used to carry the desiccant material and occupy a free-space within the IMD.
There is still a need for mechanisms that provide structural rigidity in increasingly smaller devices, limiting moisture uptake of a desiccant during manufacturing, while providing sufficient moisture uptake after sealing an IMD.